Method for controlling field flow decouple plating and a device thereof

ABSTRACT

A method for controlling plating with two independent power sources, wherein the high voltage power source is used for controlling the electrical swimming speed of the metal positive ions while the other is low-voltage power source for being used to control rate of plating rate. Positively charged metal ions of the strong electric field in the plating solution can reach to the negatively charged and unevenly distributed surface of the extraction negative pole more quickly, which is in turn connected to the negative of the low voltage power source. The ions aggregate at the recess of the extraction negative pole surface and waiting incoming electrons so as to perform electric extraction and produce uniform plating. The present invention also provides the apparatus for carrying out the mentioned method and therefore achieves better plating quality.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for controlling fieldflow decouple plating, and, in particular, to a method of controlling adecouple plating with which an electric field allowing metal ionselectrically swimming and current extracting the metal ions can becontrolled such that a coarse surface ready for being plated can becontrolled to acquire an even plating. The present invention furtherrelates to a novel plating apparatus utilizing the control method so asto enhance the quality of plating greatly.

[0003] 2. Description of Related Art

[0004] The basic theory with regard to metal plating includes a processof electrical separation process, in which metal ions moving away thesurface of the positive pole and entering the plating solution aspositive ions; a process of electrical swimming, in which the positiveions moving toward the negative in the plating solution; and a processof electrical extraction, in which the positive ions capture electronsfrom the negative pole as metal molecules adhering to the negativepoles.

[0005] Referring to FIG. 1, the earliest conventional plating apparatusincludes a rated voltage direct current power source 101, a conductivework piece 102 connecting with a negative pole and a plating metal 103connecting with a positive pole. As soon as the power is on, metalmolecules 105 of the plating metal 103 loses electrons and are ionizedas positive metal ions 106 such that the positive metal ions move towardthe work piece 102 at the negative pole to contact and obtain theelectrons so as to analyze metal molecules 104 electrically and depositon the work piece 102 due to diffusion action of ions and the electricfield in the plating solution. On the other hand, the electrolyzingreaction performs continuously so that further new metal molecules 105lose electrons to become new metal positive ions 106 to replenish theconsistency of the plating solution. The positive metal ions 106ceaselessly move toward the work piece 102 at the negative pole toelectrolyzing-extract metal molecules 104 to complete the platingprocess for the work piece due to diffusion action and electric swimmingcaused by the electric field.

[0006] The plated thickness on the work piece is varied depending on thetime duration of plating while the prior art of plating device shown inFIG. 1 is operated. The work piece at the negative pole has a surfacewith certain roughness to result in uneven plated surface while ionsbinds together with electrons in the electrolyzing-extraction process.Referring to FIG. 2, a micro view of electrolyzing-extraction process isillustrated to show the ions binding together with the electrons in caseof the work piece 102 having a coarse surface. Because the electrons inthe work piece 102 at the negative pole move faster than positive ions106 in the plating solution, the surface of the work piece 102 at theleft side thereof produces an ion void layer 107 after being plated aperiod of time and the electrons will aggregate at the surface of thework piece 102 for waiting the positive ions electrically swimming overthe void layer 107. However, the surface of the work piece 102 has acoarse extrusion 109 accumulating with more electrons 110 underactuation of the electric field. A void layer 111 at the left side ofthe tip of the jut contacts with incoming positive ions first so thatthe ions at the area of the tip has faster and more extractions. Thus, asituation of uneven plating surface occurs during the positive ionsjoining the electrons for performing the process of electrolyzingextraction such that the roughness of the plated surface is gettingrougher and the thickness of plating is getting more uneven.

[0007] Up to now, there are two ways having been proposed to improve theplating process in order to attain homogeneous plated thickness and aflat plated surface. One of the ways, which is disclosed in U.S. Pat.No. 4,789,437, is that flattering agent such as syrup is added in theplating solution. Referring to FIG. 3, the flattering agent 205 isutilized to enclose the positive ions and the positive ions enclosed bythe flattering agent excludes mutually to distribute uniformly with anequal span 202 respectively before reaching the work piece 102 at thenegative pole such that the ions 201 electrically swim toward thesurface of the work piece 102 in parallel and perpendicularly to thesurface. Being affected by the traction force of more electrons at thetip part during moving close to work piece, each positive ion becomesdeviated and moves toward tip part with the flattering agent 205enclosing each of the positive ions respectively. Because the flatteringagent 205 stays at the surface of the work piece after the ions beingelectrically extracted, the tip part will be stayed with more flatteringagent 205 due to more electrically extracted ions being produced at thetip part. Usually, the viscosity of the flattering agent is greater thanthe plating solution and the positive ions move slower in the flatteringagent than in the plating solution so that it is easier for the positiveions to arrive the recess parts on the surface of the work piece insteadof the tip part thereof. The viscosity and distribution of theflattering agent make the ions not easy to congregate at the tip partwhere the electrons congregate and force the electrically extracted ionsto distribute on the surface of the work piece evenly in order to obtainthe purpose of flattering. However, the first treatment with flatteringagent is disadvantageous that it is easy for the flattering agent to besurrounded and mixed in the extracted metal molecules 207. Although itis possible to force the flattering agent out by way of heat treatment,residue stress will be produced at the plated surface. In addition, theplating solution becomes more complicated and hard to be treated well incase of being added with the flattering agent so that the cost for thewaste solution becomes higher.

[0008] The second way for improving the plating process in order toattain homogeneous plated thickness and a flat plated surface is pulseinput power method, which has been disclosed in prior art such as U.S.Pat. Nos. 4,459,460, 3,886,053, 6,071,398, 4,789,437 and 6,132,584. Thebasic theory of operation for the pulse input method is shown in FIGS. 4to 9.

[0009] Referring to FIG. 4, a state of the pulse input power being notsupplied is illustrated. Metal positive ions 301 should be distributedevenly on the surface 305 of the work piece 102 at the negative poleunder an equilibrium condition due to the phenomenon of exclusionbetween positive electricity of ions. Referring to FIG. 5, itillustrates a state of electron current flows into the work piece 102 atthe negative pole simultaneously as soon as the pulse source is input.Because electrons in the work piece flow speedily and the heavierpositive ions move slowly. The positive ions can find out a nearestnegative pole surface 305 respectively to take an electron for beingextracted as a metal molecule 303. Referring to 6, the plating solutionon the surface of the work piece at the negative pole can form a voidlayer 305 of positive ions while the metal ions on the metal surfacehave consumed completely. Under this circumference, new electronsentering the negative pole are unable to join with the positive ionsexcept aggregating at the surface of the work piece waiting for positiveions electrically swimming from the void layer 304. Most electrons mayaggregate at the tip part 306 on the surface of the work piece due toattraction of the positive pole. Because the tip part at the surfacethereof has a thinner void layer 307 and the electrons aggregating atthe tip part can produce a local electrical field concentration 308 toattract the positive ions, the plating job after the void layer 304forming will concentrate at the tip part to coarsen the plating surfacewith inconsistent thickness. Referring to FIG. 7, a state of the pulsepower source being off supplying electrons right after the void layerforming for avoiding the electrons concentrating at the tip partawaiting positive ions is illustrated. The positive ions can be diffusedto distribute evenly so as to reach a balance naturally during the powerbeing disconnected. Then, next pulse plating can be treated after thebalance distribution. It is hard to estimate the number of the ions onthe surface of the work piece accurately during the pulse plating. Ifless ions are estimated, it results in slow plating and if excessiveions are estimated, it results in the electrons aggregating at the tippart. The conventional way is to estimate the ions excessively to admitmore electrons and the excessive electrons are removed by way of inverseimpulse. FIG. 8 shows a pulse wave signal is added with an inversepulse. The pulse plating can obtain a plating surface flatter than thatobtained by way of rated voltage. But, the ions diffusing to the surfaceof the work piece naturally is limit in speed so that the plating isslow in speed too. Further, it only can maintain the original flatnessinstead of more flat plating surface even if the plating process is thebest condition, i.e., the ions are distributed evenly. In addition, afurther disadvantage is that it needs time to switch on or off the pulsepower source instead of switching on or off instantaneously. An actualwave pattern for switching on or off the power source is shown in FIG. 9and a section of voltage rise 310 is increasing gradually withinsufficient plating current. Under the condition of insufficientplating current, the electrons will choose a position with shortestelectrical swimming distance to extract the positive ions such that itis possible to produce tip part effect. This is why the flattering agentis still utilized while the method of pulse power input is applied.

[0010] Therefore, the electrons are influenced by the electric field incase of the preceding conventional methods being used for the platingoperation so that the tip part jutting out of the surface of the workpiece at the negative pole aggregates more electrons to result in thesurface of the work piece being hard to become flat completely withprojection areas thereon getting more extending outward and recess areathereon getting more dented.

SUMMARY OF THE INVENTION

[0011] Accordingly, an object of the present invention is to provide anovel plating method, wherein the electric field and flowing current canbe adjusted independently so that the positive ions will accumulate onthe surface of the negative pole much faster than the incomingelectrons. Under the influence of the electric field, positive ions willaccumulate at the region closest to the field negative pole, where theywill wait at the recess of the plating surface for electrons to arriveso electric extraction can proceed and perform the uniform plating.

[0012] Another object of the present invention is to provide anapparatus for performing the method for controlling field flow decoupleplating so that the uneven surface of the negative pole will be flatafter the plating.

[0013] Following the plating method of this invention, the placement ofits electric poles includes a high voltage power source for the drivingfield for electrical swimming positive ions but it does not provide theplating current. The electric poles also include another low voltagehigh current power source for supplying the plating current slow and itis located at the inner of the poles of the high voltage power source.Therefore, by using the connected high voltage power source to controlthe electrical swimming speed of the positive ions to be faster than theelectrons supplied by the low voltage high current power source, morepositive ions will accumulate and await for incoming electrons so thatthe spiking effect of the electrons will not have time to occur. On theother hand, as the positive ions on the recess of the extractionnegative pole is closest to the high voltage power source's negativepole which is positioned behind the extraction negative pole, the ionswill be attracted by the static electrons of the high voltage powersource and accumulate more rapidly in the recess and perform electricextraction with the electrons. Thus, the invention makes use of the factthat electric extraction is more preferable in the recess of theextraction negative pole compared to other regions; the uneven surfaceof the work piece at the negative pole will become flat naturally by theplating method of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention can be more fully understood by referenceto the following detailed description and accompanying drawings, inwhich:

[0015]FIG. 1 is a schematic diagram of a conventional apparatus forplating illustrating an arrangement of battery power source and twoelectric poles;

[0016]FIG. 2 is an enlarged schematic diagram illustrating the surfaceroughness of the negative pole shown in FIG. 1 and a reaction structureof positive ions electrically separating the rough surface;

[0017]FIG. 3 is a schematic diagram illustrating a state with regard toelectric separating reaction of positive ion on the surface of thenegative pole after the plating solution in the conventional platingapparatus being added with flatten agent;

[0018] FIGS. 4 to 9 are schematic diagrams illustrating a series statesof reactions with regard to positive ions of an electric board beingtreated with conventional plating process under a condition of pulsepower source;

[0019]FIG. 10 is a plan view of a layout with regard to a field power,an electric separation power source and all electric poles according tothe present invention; and

[0020]FIG. 11 is a schematic diagram illustrating positive ions beingelectrically extracted between the field negative pole and theextraction negative pole shown in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] Referring to FIG. 10, the present invention includes two sets ofelectric power sources 401, 405 in the plating device constituted by thedriving field of electrical swimming and plating current. The fieldpower source 401 is a field source for producing the electrical swimmingmetal positive ions. The positive of the field power source 401 isconnected to the positive 402 of the driving field for electricalswimming, while its negative is connected to the negative of the drivingfield 403. The two electric poles 402, 403 are both covered withinsulation material 404. The driving field for electrical swimming onlyprovides the electric field for guiding the electrical swimming positiveions and does not provide the plating current. Therefore, by utilizing ahigh voltage and low current power source and insulation material 404,it will cut off the electrons from entering and thus prevent the surfaceof both positive and negative from being covered with ions or electricextraction. The plating power source 405 is used for producing theplating current. The positive pole thereof is connected to the positivepole 406 of the electrical swimming metal ions, which is located nearthe right surface of the field positive pole 402. While the negativepole 403 of the plating power source (405) is connected to theextraction negative pole 407 on the surface close to the field negativepole 403. The plating power source 405 is mainly for controlling theflow speed of the electron current, thus a low voltage and high currentpower source is being used.

[0022] According to the present invention, the respective pole of thefield power source and the plating power source are first placed intothe plating solution in a plating trough. When the field power source401 and plating power source 405 form a closed circuit, an electricalswimming electric field is established between the two electric poles402, 403 of the field power source and it is used to guide theelectrical swimming metal positive ions in the plating solution 408. Thepurpose of the plating power source 405 is to produce plating current,which will cause the positive metal ions at the extraction negative poleto gain electrons and allow the electric extraction to perform theplating process at the extraction negative pole 407.

[0023] Referring to FIG. 11, indicated in this invention, due to thepresence of the negative pole 403 of the driving field for electricalswimming, the positive metal ions are affected by it to create aflatness effect on the extraction negative pole 407 of the plating powersource 405 and thus leading to the electric extraction on the extractionnegative pole 407. In the present invention, by using a high voltageelectric field power source 401 to control the faster electricalswimming speed of the positive ions and at the same time, using lowvoltage power source 405 to control the electrical extraction rate, moremetal positive ions will accumulate on the surface of the extractionnegative pole 407 as the electrical swimming speed is faster than theplating speed. When the height (409) of the surface of the extractionnegative pole 407 is not uniform, positive ions will congregate towardsthe recess 410 of the extraction negative pole 407 under the attractionof the static electrons on the field negative pole 403, which is locatedbehind the extraction negative pole 407. This leads to the positive ionstending to move closer to the field negative pole 403 and wait for newelectron (411) to arrive on the extraction negative pole 407, in orderto carry out electric extraction. Due to the plating solution volume ofthe invention on the extraction negative pole 407 has more recessregions than projecting regions; the final result of plating will tendto be uniform across the surface and thus achieving the goal of a flatplating surface.

[0024] The main feature of the present invention is in that two controlfactors, the driving field for electrical swimming and supply of theplating current, can be independently regulated. The number of poles canbe four or it can be reduced to three in case of the two positive polesbeing combined together. The design of the circuit can also allow asingle power source to generate individually controlled current andelectrical field by way of the circuit control. It is noted that thedriving field for electrical swimming and the extraction power source inthe preceding description and in the following claims being explainedseparately is for the purpose of being understood easily. Hence, it doesnot have to provide two independent power sources and any change can bepossibly done as long as the goal of the positive ions residing in therecess of the surface of the extraction negative pole and awaiting forelectronic join and extraction can reach.

[0025] While the invention has been described with reference to apreferred embodiment thereof, it is to be understood that modificationsor variations may be easily made without departing from the spirit ofthis invention, which is defined by the appended claims.

What is claimed is:
 1. A method for controlling field flow decoupleplating, comprising following steps: a driving field for electricalswimming being produced in plating solution; a pair of ionic positivepole and extraction negative pole being connected to a plating powersource placed in the plating solution; positive metal ions on the ionicpositive pole being controlled by the driving field for electricalswimming to move towards the extraction negative pole and the electricextraction taking place at a recess on the extraction negative polesurface.
 2. The method for controlling field flow decouple platingaccording to claim 1, wherein the driving field for electrical swimmingcomprises a field positive pole and a field negative pole that areconnected to a high voltage electric field power source and placed awayfrom each other in the plating solution as well.
 3. The method forcontrolling field flow decouple plating according to claim 1, whereinthe ionic positive pole and the extraction negative pole in between theelectric poles of the driving field for electrical swimming areconnected to the corresponding positive and negative field poles.
 4. Anapparatus of field flow decouple plating, comprising: a high voltagedirect current power source for a driving field with electricalswimming, providing a first positive pole and a first negative pole; alow voltage plating direct current power source, providing a secondpositive pole and a second negative pole; plating solution, containing adriving positive pole and a driving negative pole for electricalswimming and the driving positive pole spacing apart from the drivingnegative pole, a driving positive pole and a driving negative pole forelectric swimming, and a metal ionic positive pole and an extractionnegative pole; wherein, the first positive and first negative poles areconnected to the driving positive pole and the driving negative polerespectively, the second positive pole is connected to the metal ionicpositive pole and the second negative pole to the extraction negativepole, and the metal ionic positive pole and the extraction negative poleare disposed to oppose to the driving positive pole and the drivingnegative pole for electrical swimming respectively.
 5. The apparatus offield flow decouple plating according to claim 4, wherein the firstpositive pole and the first negative pole are covered with insulationmaterial.